1. Field of the Invention
This invention relates to a magnetic record member for use in magnetic recording devices, such as a magnetic disk or a magnetic drum.
2. Description of the Prior Art
Generally, recording and reproducing systems employed in magnetic recording devices equipped with a recording/reproducing head (hereinafter referred to as a head) and a magnetic record member may be classified into the following two systems. The first is known as a contact-start-stop (CSS) system which is operated by setting a head in contact with the surface of a magnetic record member at the start of operation, subsequently rotating the record member at a predetermined speed in such a manner as to form an air-film space between the head and the record member surface, and performing a recording or playback action while maintaining such space. According to the CSS system, the rotating magnetic record member is stopped simultaneously with termination of the operation, and the magnetic head is maintained in frictional contact again with the record member surface as at the start of the operation.
The second type of system is operated by abruptly pressing a head onto the surface of the record member which is already rotating at a predetermined speed, to form an air-film space therebetween, and performing a recording or reproducing action while maintaining such space.
In the first system, the head and the record member surface are kept in frictional contact with each other both prior to the start and after the end of the operation while in the second system, the head is brought into contact with the record member surface only when pressed thereto during operation. The frictional force exerted between the head and the record member surface while in this state of mutual contact causes wear of both the head and the record member and may finally damage the head and a magnetic-metal thin film medium formed on the record member. Moreover, even a slight variation in the attitude of the head in such a state of frictional contact results in a nonuniform load imposed on the head and might therefore damage the head and the record member surface. Furthermore, during the recording or reproducing operation, in those cases where the head suddenly and unexpectedly contacts the surface of the magnetic record member, a large frictional force is exerted between the head and the record member which may damage both or cause a breakdown thereof.
For the purpose of protecting the head and the magnetic record member from such friction as well as from such wear and breakdown resulting from this mutual contact, it is necessary to coat the surface of the record member with a protective film. For example, a plated metallic film such as Cr, Rh or Ni-P is conventionally employed. However, this film does not effectively solve the problems associated with the above-described frictional contact.
Another protective film is proposed in U.S. Pat. No. 3,466,156 which consists of a synthetic polymer thin film on a magnetic-metal thin film medium and of a wax film coated on said polymer thin film. However, the adhesion between each of these two films and the individual underlayer thereof is insufficient, with the result being that each film is peeled off from the underlayer as a result of repeated or strong frictional contacts between the head and the magnetic record member, and eventually this arrangement is not suited for practical use either.
Moreover, still another protective film is disclosed in U.S. Pat. No. 3,719,525 which is formed by oxidizing the surface of a magnetic-metal thin film medium and applying a silicone oil thereto. This protective film is, however, disadvantageous in that the magnetic characteristics of the thin film medium are deteriorated and an undesirable adhesion phenomenon occurs between the head and the disk, hence failing to serve as an effective means to eliminate the problem of frictional contact and therefore is unpractical.
The present inventor has previously proposed a magnetic record member wherein a magnetic-metal thin film medium is coated with a film composed of a hydrolysis polymer of a polysilicate or metal alkoxide, and another magnetic record member where a layer of an oriented lubricant is further formed on such a hydrolysis polymer film (see U.S. Pat. No. 4,069,360 and copending, commonly-assigned, U.S. patent applications Ser. Nos. 844,623 and 860,832, filed Oct. 25, 1977 and Dec. 15, 1977, respectively). Although each of these two inventions is capable of protecting the magnetic record member from the above-mentioned phenomenon of frictional contact, the reliability against such phenomenon is required to be as high as possible.